1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and method of integration of titanium and titanium nitride layers.
2. Description of the Related Art
Reliably producing sub-micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large scale integration (ULSI) of semiconductor devices. However, as the fringes of circuit technology are pressed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on the processing capabilities. The multilevel interconnects that lie at the heart of this technology require precise processing of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects is very important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates.
As circuit densities increase, the widths of interconnects, such as vias, trenches, contacts, and other features, as well as the dielectric materials between, decrease to sub-micron dimensions (e.g., 0.20 micrometers or less), whereas the thickness of the dielectric layers remain substantially constant, with the result of increasing the aspect ratios (i.e., height divided by width) of the features. Many traditional deposition processes have difficulty filling sub-micron structures where the aspect ratio exceeds 4:1. Therefore, there is a great amount of ongoing effort being directed at the formation of substantially void-free and seam-free sub-micron features having high aspect ratios.
In the manufacture of integrated circuits, a titanium/titanium (Ti/TiN) film stack, a titanium nitride layer over a titanium layer, is often used as a liner barrier. For example, Ti/TiN film stack may be used to provide contacts to the source and drain of a transistor. For example, a Ti layer is deposited over a silicon substrate. A portion of the Ti layer, which is in contact with the silicon substrate, is converted to titanium silicide (TiSix) in situ or in an annealing step. A TiN layer is deposited over the Ti layer. The titanium nitride layer is used as a barrier layer to inhibit the diffusion of metals into regions underlying the barrier layer. A metal layer, such as a tungsten layer, is deposited over the TiN layer.
A Ti layer and a TiN layer may be formed by chemical vapor deposition and/or physical vapor deposition techniques. One example of forming a Ti Layer by chemical vapor deposition includes reacting titanium tetrachloride (TiCl4) with a hydrogen plasma. One example of forming a TiN layer by chemical vapor deposition includes reacting TiCl4 with a nitrogen reactant, such as a nitrogen plasma or ammonia (NH3). One problem with the use of TiCl4-based chemistry used to form a TiN layer over a Ti layer is that reliability problems can occur. In particular, the TiN layer may have poor adhesion over the Ti layer, resulting in peeling of the TiN layer off the Ti layer.
Therefore, there is a need for an improved apparatus and method of integration of titanium and titanium nitride layers.